If morality is a natural feature of society, should we not give it a great deal of examination?
Several themes, such as the incorrectness of murder, are part of all societies. There is a variety of differences in the values held by separate societies. It is in these differences, and/or lack of knowing/understanding of the correct ethical construct that we find the conflicts in our human history.
Normative Ethical Principles and Theories: A Brief Overview http://www.stedwards.edu/ursery/norm.htm
Introduction to Ethics
from http://instruct.westvalley.edu/lafave/INTROETH.HTM